Pop-up irrigation sprinklers are typically buried in the ground and include a stationary housing and a riser assembly, mounted within the housing, that cycles up and down during an irrigation cycle. During an irrigation cycle, the riser assembly is propelled through an open upper end of the housing and projects above ground level, or “pops up,” to distribute water to surrounding terrain. More specifically, pressurized water is supplied to the sprinkler through a water supply line attached to an inlet of the housing. The pressurized water causes the riser assembly to travel upwards against the bias of a spring to the elevated spraying position above the sprinkler housing to distribute water to surrounding terrain through one or more spray nozzles. When the irrigation cycle is completed, the pressurized water supply is shut off and the riser is spring-retracted back into the sprinkler housing so that the housing and riser assembly are again at and below ground level.
A rotary sprinkler commonly includes a rotatable turret mounted at the upper end of the riser assembly. The turret includes one or more spray nozzles for distributing water and is rotated through an adjustable arcuate water distribution pattern. There are also other types of pop-up sprinklers that operate without the rotating turret.
Rotary sprinklers commonly include a water-driven motor to transfer energy of the incoming water into a source of power to rotate the turret. One common mechanism uses a water-driven turbine and a gear reduction system to convert the high speed rotation of the turbine into relatively low speed turret rotation. Some examples of rotary sprinklers include the sprinklers described in U.S. Pat. Nos. 4,625,914; 4,787,558; 5,383,600; 6,732,950; and 6,929,194; all assigned to the assignee of this application, Rain Bird Corporation.
During normal operation, the riser reciprocates within the stationary housing as water pressure in the supply line increases and decreases. When the water pressure is low, a spring biases the riser down. When water pressure increases, the water pressure overcomes the spring bias and the riser pops up. Except for when the riser is translating, the riser position is usually in one of two positions: fully extended or fully retracted.
Rotary sprinklers commonly employ a wiper seal within the housing that engages an outer surface of the riser. When the sprinkler is in the off position, an annular wiper blade disposed at ground level prevents grit and dirt from entering the housing. When the sprinkler is in the on position, the annular wiper blade continues to engage the outer surface. As the riser retracts, the annular wiper blade scrapes debris from the outer surface of the riser. Additionally, the annular wiper blade prevents water from exiting between the riser and a cover attached to the housing, and also prevents water from leaking where the cover engages the housing, thus conserving water.
Prior designs of the wiper seal included the annular wiper blade disposed at the top of the housing, and a sealing blade disposed within the housing. The annular wiper blade primarily operates to prevent grit from entering the housing, while the sealing blade controls bypass flow. Bypass flow is water that does not exit the sprinkler through the nozzle but, rather, exits the sprinkler from the gap between the wiper seal and the riser assembly. When the riser is fully elevated, the sealing blade contacts a flared end of the riser, creating a water-tight seal and substantially preventing bypass flow from exiting the cavity. However, before the riser assembly is fully elevated, there is an insufficient seal to prevent bypass flow.
The annular wiper blade of the prior designs has an interior diameter that is approximately equal to the outside diameter of the riser, but it does not create a tight seal in order to allow the riser assembly to reciprocate within the housing. As the riser reciprocates in and out of the housing when the sprinkler turns off and on, respectively, friction is created between the annular wiper blade and the riser assembly. Over time, the annular wiper blade wears down because of the repeated friction. The sealing blade of prior designs has an interior diameter that is slightly larger than outer diameter of the riser assembly, and seals against the flared end of the riser assembly when the riser assembly is fully extracted. Before sealing, however, the gap between the sealing blade and the riser assembly allows a high amount of bypass flow. Repeated sealing and unsealing between the sealing blade and the riser contributes to the sealing blade wearing down over time.
As the annular wiper blade and sealing blade wear down, it increases the area between the riser and the wiper seal. This increases the amount of bypass flow that occurs, which allows any grit that has managed to enter the cavity to be pulled up and toward the wiper seal. This can result in the grit becoming lodged between the wiper seal and the riser. Excess grit and debris in this area further contributes to the bypass flow problem by preventing the sealing blade from properly sealing against the riser. This can create relatively large leaks and also can prevent the sprinkler from retracting if too much grit is lodged between the wiper seal and the riser. The grit can also permanently damage the wiper seal causing additional leaks. Leaks result in water loss across the irrigation network. Limiting water loss is important as water resources are becoming more limited and restrictions on water use are increasing.
When the bypass flow increases, additional water pressure is necessary to overcome the spring bias. Over time, this can result in complete failure of the sprinkler to pop up when the water pressure is not high enough to overcome the spring bias. Additionally, exemplary irrigation systems include a plurality of sprinklers disposed along the water supply line. If too many sprinklers allow bypass flow to exit the cavity, other sprinklers on the system may not receive adequate inlet pressure to overcome the spring bias, even when they are not suffering the bypass flow problem.
Therefore, there is a need for a pop-up sprinkler device that prevents bypass flow. Further, there is a need for a wiper seal that is more resistant to wear after repeated reciprocation of the riser, that prevents leaking to conserve water, and that fully extracts and retracts with high reliability.